Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/07—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing phosphates
  • C23C22/08—Orthophosphates
  • C23C22/12—Orthophosphates containing zinc cations
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
  • F24S70/00—Details of absorbing elements
  • F24S70/20—Details of absorbing elements characterised by absorbing coatings; characterised by surface treatment for increasing absorption
  • F24S70/225—Details of absorbing elements characterised by absorbing coatings; characterised by surface treatment for increasing absorption for spectrally selective absorption
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
  • F24S70/00—Details of absorbing elements
  • F24S70/20—Details of absorbing elements characterised by absorbing coatings; characterised by surface treatment for increasing absorption
  • F24S70/25—Coatings made of metallic material
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E10/00—Energy generation through renewable energy sources
  • Y02E10/40—Solar thermal energy, e.g. solar towers

Definitions

• the invention relates to a process for producing a black coating on at least one face of metal parts, in particular panels, this face being formed of pure or alloyed zinc.
• the invention was born within the framework of researches of improvements of solar collectors. These are, currently, very generally constituted by panels of slightly corrodible metal, such as stainless steel, copper or aluminum, provided with a heat transfer fluid circuit, and presenting to solar radiation a surface carrying a black covering (c (i.e. absorbent for radiation).
• a black covering i.e. absorbent for radiation.
• the absorption coefficient of the covering in the range of energy wavelengths of the solar radiation and the thermal impedance between this covering and the heat transfer fluid circuit determine the efficiency of the sensor, as a function of the density of radiation received and of the temperature of the heat transfer fluid, and consequently the conditions under which the yield is canceled, and therefore the duration of effectiveness of the solar collector in the day and seasonal cycles.
• the energy requirements which must be met by solar collectors are significant, especially when the density of solar radiation is low, so that improvements, at first sight of little importance, in the absorption coefficient of the coating, currently often between 0.9 and 0.95, and the thermal impedance between coating and heat transfer fluid, may ultimately prove to be of major interest.
• the commonly used solution of a coating of matt black paint on aluminum or copper has a relatively high thermal impedance despite the use of metals which are good conductors, this impedance being located in the thickness of the paint and at the interface. between the paint and the underlying metal.
• the Applicant sought to develop a process for the production of an adherent black coating.
• zinc coefficient absorption greater than 0.95, in itself a good conductor of heat and forming a low thermal impedance at the interface with the zinc galvanizing layer.
• the adhesion to zinc and the low thermal impedance of interface, in joint conditions almost necessarily imply a bond of the coating on the zinc which brings into play the specific properties of zinc; as a corollary, the process will be effective on any part having a zinc face, whether the part is made of solid zinc, or of any metal masked by the zinc layer.
• the invention also proposes a method for producing a black coating on at least one face of metal parts, in particular panels, this face being formed of pure or alloyed zinc, characterized in that said face is brought into contact, at a temperature between ambient and 75 ° C and for a period between 120 and 5 seconds, with an aqueous solution containing from 3 to 25 g / 1 of cupric ions, from 5 to 25 g / 1 of ions zinc, from 1 to 20 g / 1 of nickel ions, from 15 to 40 g / 1 of orthophosphoric ions, and optionally anions not capable of forming insoluble salts with the aforementioned metal ions, the pH of the solution being understood between 1.6 and 3.0, and the part is cleaned after the end of the contact time.
• the cleaning of the part is carried out by washing to remove residual traces of solution, drying then brushing to remove loose particles on the face of the coin.
• the duration and the contact temperature will be chosen taking into account that the higher the reaction temperature, the higher the reaction speed. It will be admitted that the contact time is reduced by half by a temperature rise of between 8 and 16 ° C.
• the solution will contain from 5 to 18 g / 1 of cupric ions, from 8 to 9.5 g / 1 of zinc ions, from 4 to 8.5 g / 1 of nickel ions and from 20 to 30 g / 1 of orthophosphoric ions, the pH being between 1.8 and 2.4. More particularly, the content of cupric ions will be between 11 and 14 g / l, and the content of nickel ions between 6.5 and 8.5 g / l.
• the solutions prepared according to the previous examples have very similar behaviors on zinc sheets immersed in these solutions at a temperature of 20 ° C for a period of 90 seconds.
• the black deposit layer has a thickness of approximately 10 ⁇ m, and the absorption coefficient is close to 0.97.
• the contents of the constituents can vary within wide limits without the absorption properties of the black coating being impaired.
• the content of cupric ions can vary from 3 to 25 g / 1, the content of zinc ions between 5 and 25 g / 1, the content of nickel ions between 1 and 20 g / 1, the content of orthophosphoric ions between 15 and 40 g / 1, while the pH could vary between 1.6 and 3.0.
• the contents of Cl - or SO 4 2 - ions are practically any, taking into account that these ions come from copper and nickel salts. It is moreover clear that these anions, which do not participate in the reactions, are chosen for their convenience of use as soluble salts and do not give precipitates with the cations present, and their availability.
• the tests then focused on the conditions of use of the darkening solutions, method of application, duration and contact temperature.
• reaction rates increase exponentially with temperature.
• the temperature range which halved the reaction time was determined to be between 8 and 16 ° C. At temperatures below 15 ° C, reaction times exceed 120 seconds.
• durations are reduced to less than 5 seconds (between 60 ° and 75 ° C)
• the control of the duration becomes difficult, and the reactions are likely to get carried away: in addition the heating of the solutions and the parts is expensive.
• the black coating is porous, so that in the presence of moisture the underlying zinc is liable to oxidize, corrosion manifested by the appearance whitish spots.
• glazing it is common for solar panels to have glazing to promote the so-called "greenhouse” effect, the glazing being transparent to infrared radiated by the sun, and opaque to long infrared corresponding to the temperature of the panel.
• the glazing makes it possible to constitute a watertight box where corrosion by humidity is not to be feared. In the absence of a glazed box, it is recommended to subject the coating ment and the zinc underlying a passivation treatment, or covering the coating with a protective varnish, or the like.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• General Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Sustainable Energy (AREA)
• Sustainable Development (AREA)
• Life Sciences & Earth Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Organic Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Metallurgy (AREA)
• Materials Engineering (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Chemical Treatment Of Metals (AREA)
• Application Of Or Painting With Fluid Materials (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (3)

Family

ID=9265518

Family Applications (1)

Country Status (4)

Cited By (1)

Family Cites Families (5)

• 1981
  • 1981-12-30 FR FR8124487A patent/FR2519028A1/fr active Granted
• 1982
  • 1982-12-14 AT AT82402283T patent/ATE28336T1/de not_active IP Right Cessation
  • 1982-12-14 EP EP82402283A patent/EP0083263B1/de not_active Expired
  • 1982-12-14 DE DE8282402283T patent/DE3276761D1/de not_active Expired

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